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In many engineering applications, repeated wetting and drying is one of the most destructive processes which can lead to continuous damage to in situ rocks. Worse still, the situation is exacerbated if the action is coupled with flowing water conditions. In this work, the effects of wetting–drying (W-D) cycles on the failure characteristics of tunnels excavated in the gypsiferous strata were investigated by using the particle flow code. The meso-mechanical parameters of gypsiferous rock models under different W-D cycles at different flow rates (0, 10, and 20 l/h) were determined by the trial-and-error method. A two-dimensional 1/180 scale model of the tunnel was established based on the working principle of centrifuge. The evolution characteristics of force chains and fractures in the excavation disturbance zone (EDZ) under different conditions of W-D cycles and flow rates were analyzed. Furthermore, the formation mechanism of the problems in the South Lvliang Mountain Tunnel was discussed, and some prevention measures were suggested. The results showed that with increasing W-D cycles and flow rates, the fractures and disappearance zones of force chains in the EDZ gradually increase, while the influence of flow rates on their distribution becomes significant. With increasing W-D cycles and flow rates, under the unsupported condition, the development characteristics of growth curves of fractures will gradually transition from “rapid growth to stability” to “rapid growth to slow growth.” Under the support condition, the development characteristics of growth curves of fractures will gradually transition from “rapid growth to stability” to “rapid growth to fluctuating growth, and then stability,” and then to “rapid growth to slow growth, and then rapid fluctuating growth.” The flow rates will greatly accelerate the deterioration of surrounding rocks caused by the action of W-D cycles, thus causing the lining damage in a shorter time. [ABSTRACT FROM AUTHOR]

The cyclic wetting-drying (W-D) phenomenon, which is a part of weathering processes, plays a vitally important role in affecting rock materials' properties. In this paper, the gypsum breccia, an environmentally sensitive rock, was taken as the research object, which has the characteristics of high solubility. The deterioration behavior of gypsum breccia under W-D cycles with different flow rates was investigated. A one-dimensional water saturation test was conducted to study the coupling mechanism of water saturation-dissolution of gypsum breccia. A series of W-D cycle tests with different flow rates (0, 10, and 20 l/h) for gypsum breccia were conducted to reveal its deterioration behavior. Furthermore, the influence of these effects on the stability of the tunnel was discussed. The results show that gypsum breccia has a coupling behavior of water saturation and dissolution in the water environment. The effect of W-D cycles is the primary reason for the formation of visible cracks in gypsum breccia, while the flowing water will wash away the loose particles caused by the action of W-D cycles and accelerate the development of visible cracks and dissolution in gypsum breccia. The combination of these two actions gradually deteriorates the self-stability of the surrounding rock, which eventually leads to lining damage due to overload. The study can provide references for the engineering design of tunnels in gypsum breccia. [ABSTRACT FROM AUTHOR]